Gold alloy plating



United States Patent GOLD ALLOY PLATING Silvio C. Taormina, Flushing, N. Y., Alfred T. Marinaro, Newark, N. J., and Louis Packrnan, Brooklyn, N. Y., assiguors to Platers Research Corporation, New York, N. Y., a corporation of New York No Drawing. Application February 7, 1951, Serial No. 209,908

Claims. (Cl. 20443) This invention relates to gold plating by electro-deposition and is more particularly concerned with the depositions of gold and other metals from the same plating bath to obtain a plate having improved characteristics.

The type of plating is that which is adapted for use in decorative gold plating such as the jewelry and related trades wherein the thickness of the plate may vary from a flash coloring obtained by as little as several seconds of electroplating to a plate having a thickness of 0.005 of an inch.

An important object of this invention is to achieve a gold plate which is extremely resistant to abrasion.

Another object is to provide a more economical gold plate by virtue of the saving of gold effected by reducing the thickness of plate necessary to yield a gold plate having a given period of service.

Another object is to provide a gold plate having certain improved coloration.

A still further object is to provide a type of gold plating solution which will yield a gold plate having a relatively constant and stable coloration.

The invention consists of improving the characteristics of a gold plate as applied by electrodeposition by the addition of soluble compounds of uranium or soluble compounds of molybdenum to an aqueous gold plating solution. It has been determined by spectrographic analysis that the metal coating electrodeposition from the solution, at the cathode, consists of gold together with the metallic elements of said soluble compounds and that such gold plates are considerably more wear and abrasive resistant than gold plates which do not contain the uranium or the molybdenum but which were deposited under similar conditions.

In the practice of this invention, the salts of either uranium, molybdenum, or both are added to an aqueous gold plate bath, such as a cyanide bath. Electroplating is thereafter carried forward in the usual manner. By varying the amounts of the soluble compounds of uranium and molybdenum which are added to the bath, the amounts of those metals in the final plate may be varied and the resulting color of the plate may also be varied. Increasing the uranium content in the gold plate changes the color of the gold from yellow to light yellow, pink, white Hamilton, light purple and finally to a dark purple which is almost black. The darker hues of the gold plates are obtained from solutions having high proportionate uranium content and by increasing the temperature of the solution and also by increasing the current density. When molybdenum is present in the gold plate, the plate will have a light colored gold hue similar to that known in the trade as Hamilton gold, i. e. a light gold, between white and yellow. The hue achieved with molybdenum is stable and does not vary appreciably as the amounts of the molybdenum compound present in the plating solution are changed. The use of the soluble molybdenum compound in commercial gold plating solutions is therefore particularly 2,754,258 Ce Patented July 10, 1956 Solution 1 Spectrographie Analysis of Plate .0003 of inch ick Water:

i i 'tr iti t i it otass um 0 y a e, rams per i er F111}? Potassium Cyanide, 1.5 Grams per g fi f constituent 1 er. Potassium Hydroxide, 7% Grams per Molybdenum liter.

Solution II Spectrographic Analysis of Plate .0003 of inch thick Water:

Ilime GiollIdfl l l ralmsG per liter. .f

rany ra e, 5 rams per iter Gold Potassium Carbonate 30 Grams per literv over Frnee Potassium Cyanide, 4 Grams per Uramum 05-10% ter.

Solution III Spectrographic Analysis of Plate .0003 of inch thick Water:

Fine Gold, 4 Grams per liter Molybdenum Trioxide, 2 Grams per liter. Free Potassium Cyanide, l5 Grams per Ii 1. Gold, over 90%. P 1 ttassium Hydroxide, 7% Grams per Molybdenum .005.05%.

1 er. N iekel Cyanide, 2 Grams per liter Zinc Cyanide, 1.5 Grams per liter Solution IV Spectrographic Analysis of Plate .0003 of inch thick Water:

Fine Gold, 4.0 Grams per liter Uranyl acetate, 2.0 Grams per liter Free Potassium Cyanide, 15.0 Grams per liter. Gold, over Free lPtotassium Hydroxide, 7.5 Grams Uranium 1-5%.

per 1 er. Pilitassium Carbonate, 300 Grams per iter.

In plating from Solutions I, II, III and IV, the solutions in each case were made up in one liter of water, the anode used was stainless steel, the cathode was polished nickel, the current density was 15 amps./sq. ft. and the plating time was 30 minutes. The solutions were maintained between th temperature limits of 65 C. to 75 C. The plate obtained from these tests averages about 0.0003 inch in thickness. The spectrographic analyses of the plates deposited from Solution II indicated that uranium was deposited with the gold, and that the plate deposited from Solutions I and III showed that molybdenum was deposited with the gold and that the plate from Solution III also contained amounts of nickel and zinc. The plate obtained from Solution I had a Hamilton gold color, Solutions II and IV had a Hamilton-pink gold color, and Solution IH had a Hamilton Representative solution Water: Grams per liter Fine gold 4 Free potassium cyanide 7.5 Copper cyanide 2 Nickel cyanide 10 Potassium ferrocyanide 10 The representative solution yields a gold plate which is known generally as a Hamilton 14K.

The plates resulting from Solutions I, II, III and IV and the plate resulting from the representative gold plate solution were compared by subjecting them to abrasion by steel balls in a tumbling barrel. Gold plates produced from Solutions I, II, III and IV required between 30 to 60 minutes to burnish to a selected standard limit while those plates produced by the representative gold solution required only to minutes to burnish to the same degree; such tests accordingly demonstrated that wear resistance is enhanced approximately six-fold.

As noted above the characteristic yellow gold color which results when molybdenum is combined with gold has a relatively stable hue which does not change in character with variations in the amounts of soluble molybdenum compounds present in the plating solution. For example, the color of the plate resulting from Solutions I and III was substantially the same hue although the Solution I contained 4 grams of potassium molybdate per liter and Solution III contained 2 grams of molybdenum trioxide per liter. Spectrographic analysis of the plates resulting from Solutions I and III indicated that the molybdenum was present in the plate in substantially the same proportions even though the ratio of the molybdenum compound in the plate solution was substantially varied with respect to the amount of gold present in the solution.

Other soluble compounds of uranium and molybdenum which may be used in plating solutions effectively are:

Uranium phosphate Uranium oxalate Uranium benzoate Metauranic acid Molybdenum hydroxide Molybdenum dihydroxytetrachloride Molybdenum oxydichloride Molybdenum thiocyanate Molybdic acid Gold plates containing molybdenum and uranium are more wear resistant and still maintain the colorations or have more desirable colorations than those presently obtainable and at the same time the plate contains sufficient gold to meet the standard requirements of electroplated gold. With the present invention, a gold plate of 0.00002 inch in thickness may be applied to an article and will have the same or greater wearing characteristics and useful life than a gold plate obtained of 0.00005 inch in thickness from the representative solution noted above. The cost of the final platebecause of reduced plating time and because of less gold used is less than half of the cost of applying the thicker plate from the presently known gold plating solutions such as the plate from the representative solution. By the use of the invention a saving of at least 50% can be effected.

In addition to the saving in cost resulting from the use of a thinner gold plate, the more abrasive resistant.

gold plate of this invention will provide a surface which will retain its original lustre longer and will be less subject to scratching than the gold plates which are presently in use.

Having thus described my invention, I claim:

1. An electrodeposited surface containing over of gold and molybdenum in the range of .005 to .05% and characterized by a resistance to abrasion greater than a surface of the same gold content but which is free of molybdenum.

2. An electrodeposited surface having 9095% gold and .05 to 5% uranium.

3. An electrodeposited surface containing over 90% of gold and uranium in the range of .05 to 5% characterized by a resistance to abrasion greater than a surface of the same gold content but which is free of uranium, and by a Hamilton-pink gold color.

4. An electroplating cyanide bath containing water, 4 grams per liter of fine gold, 15 grams per liter of free potassium cyanide, 4 grams per liter of potassium molybdate, 7 /2 grams per liter of potassium hydroxide.

5. An electroplating cyanide bath containing water, 4 grams per liter of fine gold, 30 grams per liter of potassium carbonate, 15 grams per liter of free potassium cyanide, 4 grams per liter of uranium nitrate.

6. An electroplating cyanide bath containing water, 4 grams per liter of fine gold, 15 grams per liter of free potassium cyanide, 7%. grams per liter of potassium hydroxide, 2 grams per liter of molybdenum trioxide, 2 grams per liter of nickel cyanide, 1.5 grams per liter of zinc cyanide.

7. An electroplating cyanide bath containing water, 4 grams per liter of fine gold, 15 grams per liter of free potassium cyanide, 7 /2 grams per liter of free potassium hydroxide, 30 grams per liter of potassium carbonate, 2 grams per liter of uranium acetate.

8. An electrodeposited surface containing over 90% gold with at least one metal from the group consisting of molybdenum and uranium, in the amount of about .05%, and characterized by a resistance to abrasion greater than a surface of the same gold content but which is free of molybdenum and uranium.

9. The method of producing an electrodeposited surface containing over 90% gold and uranium in the range of .05 to 5% on an article comprising, immersing said article in a gold cyanide bath containing water and 4 grams per liter of fine gold, 30 grams per liter of potassium carbonate, 15 grams per liter of free potassium cyanide, and 4 grams per liter of uranium nitrate, using said article as a cathode, and passing an electric current between said article and an anode disposed in the bath.

10. The method of producing an electrodeposited surface containing over 90% gold and uranium in the range of .05 to 5% on an article comprising, immersing said article in a gold cyanide bath containing water and 4 grams per liter of fine gold, 15 grams per liter of free potassium cyanide, 7 /2 grams per liter of free potassium hydroxide, 30 grams per liter of potassium carbonate, and 2 grams per liter of uranium acetate, using said article as a cathode, and passing an electric current between said article and an anode disposed in the bath.

References Cited in the file of this patent UNITED STATES PATENTS 231,064 Linsenmayer Aug. 10, 1880 1,248,621 Cooper Dec. 4, 1917 1,962,859 Dietz June 12, 1934 2,147,637 Golyer Feb. 21, 1939 2,259,270 Ryder Oct. 14, 1941 2,303,497 Reeve Dec. 1, 1942 2,516,227 Ma July 25, 1950 OTHER REFERENCES Pritchard: Metal Industry, vol. 31, No. 12 (Decemb 19 3)., ,P- 403.- 

4. AN ELECTROPLATING CYANIDE BATH CONTAINING WATER, 4 GRAMS PER LITER OF FINE GOLD, 15 GRAMS PER LITER OF FREE POTASSIUM CYANIDE, 4 GRAMS PER LITER OF POTASSIUM MOLYBDATE, 71/2 GRAMS PER LITER OF PATASSIUM HYDROXIDE.
 5. AN ELECTOPLATING CYANIDE BATH CONTAINING WATER, 4 GRAMS PER LITER OF FINE GOLD, 30 GRAMS PER LITER OF POTASSIUM CARBONATE, 15 GRAMS PER LITER OF FREE POTASSIUM CYANIDE, 4 GRAMS PER LITER OF URANIUM NITRATE. 